Electrokinetic-based air cleaning systems have been developed and formerly commercialized in the United States by the company Sharper Image under the trade name Ionic Breeze. The original electrokinetic principle was enunciated by Brown in U.S. Pat. No. 2,949,550. This was further improved by Lee in U.S. Pat. No. 4,789,801 for improving airflow and minimizing ozone generation by voltage control. In addition, Lee in U.S. Pat. No. 6,603,268 described methods for coating electrodes with catalyst to destroy the ozone generated. It is well-known that MnO2 is an effective catalyst for conversion of O3 to O2 and is not consumed in the process. Ozone is catalytically degraded according to the process shown in FIG. 10. Thus, the manganese dioxide is not consumed in the process and can be re-used indefinitely.
Strategies have been described for reduction of ozone produced by ionic propulsion such as Lee et al U.S. Pat. No. 4,789,801. Sharper Image also commercialized a post-market device for removal of ozone, the Ozone Guard, which clamped on the outlet and has a metal honeycomb structure which likely was coated with catalyst. In the foregoing descriptions of devices using electrokinetic propulsion, a common element is a high voltage electrode consisting of a wire. A very steep voltage gradient is generated orthogonally to the wire because of the very small cross-sectional area of the wire. The high voltage gradient causes the creation of a plasma consisting of charged particles, and kinetic energy is imparted to the charged particles by the high voltage gradient. The resulting net air flow is created by exchange of kinetic energy between charged and uncharged particles, and the net air flow is directed by the juxtaposition of planar electrodes which are at zero or opposite sign voltage to that of the wire electrode. Charged particles are electrostatically precipitated on to the planar electrodes, which may periodically be removed for cleaning. As first described by Custis et al (Cin. Exp. Allergy 2003, 33, 986-991), the Ionic Breeze device has been adapted for sample collection for allergen analysis by wiping down the electrodes with a paper tissue. The allergens were extracted from the tissue and subject to an immuno-assay. The Ionic Breeze was also used in the works of Peters et al (J. Urban Health 2007, 84, 185-197) and Platts-Mills et al (J. Allergy & Clin. Immunol. 2005, 116, 384-389) for allergen collection for immunoassay analysis. More recent work has focused on the adaptation of a small device with optimized electrode configuration for efficiently collecting samples for testing (Gordon et al. American Association for Aerosol Research. 2013. http://aaarabstracts.com/2013/viewabstract.php?pid=35; Gordon J, J. Allergy Clin. Immunol, (2012) 129(2):AB92-AB92; Gordon et al (2013), J. Allergy Clin. Immunol. 131(2):AB76-AB76; Gordon et al (2014). J. Allergy Clin. Immunol. 133(2):AB187-AB187; Gandhi, et al, (2015) Journal of Allergy and Clinical Immunology, Vol. 135, Issue 2, AB384; Gordon et al (2015) Journal of Allergy and Clinical Immunology, Vol. 135, Issue 2). It is particularly important that such devices do not emit irritating substances such as ozone since they may be run in the presence of patients who have respiratory disorders and thus be particularly susceptible. Tatsushima and Sukura in U.S. Pat. No. 4,871,709 describe methods for fabrication of ozone cracking catalysts with fine structure that provides low resistance to flow, but do not anticipate applications to ion-propulsion devices.
In spite of efforts to limit ozone emission, the commercial devices were unsuccessful. Described herein is a device and method of applying catalysts to ionic propulsion devices in such a way that ozone can be essentially eliminated from the effluent air without compromising flow rate.